Treating fatty acids



June 13, 1944. A' ,.A. H. zExGLER ET A1. 2,351,249

TREATING FATTY ACIDS lFiled sept. 28, .1940

orzdcinser rWier l Patented June 13,v 1944l` FFICE TREATIN G FATTY ACIDSAlbert H. Zeigler, Evanston, Dale V.

Downers Grove, and James M. Kiefer, Ill., assignors to Armour andCompany, Chicago, Ill.. a corporation of Illinois l Stingley. Chicago,

ApplicationV September 28, 1940, Serial No. 358,792

7 Claims. (Cl- 2oz-62) In the practice heretofore employed forfractionally distilling fatty acids to effect a separa- Vtion thereofsubstantially according to boiling point, the saturated and unsaturatedfractions have been treated snnultaneously.Y lwhiley'a" vacuum of mm.can be maintained at the top of the fractionating tower, the pressure atthe aA-bottomofg the tower, due to the large number of bubble trays bymeansof which the upwardly rising fatty acid vapors contact thedownwardly owing reflux liquid fatty acids, is ofthe order of 35 to 40mm. mercury absolute. Because of the higher pressure in the lowerportion of the tower, relatively high temperatures have to be tion andthen subsequently fractionally distilling the two products separately toseparate the L acids substantially according to chain length.

employed such as, for example, temperatures of the order of 240C.Furthermore, since fractional distillation involves the returning ofsubstantial amounts of fatty-acid as reux, the heat input at the base ofthe tower must be from two to iive times as much asthat necessary forstraight distillation. With such higher temperatures and with theincreased required amount ofheat input, unsaturated fatty acids aresubject to considerable thermo-alteration. Since unsaturated fractionsof fatty acids are extremely desirable for use in paints, varnlshes,lacquers, baking and air drying enamels, etc., a considerable loss isencountered through the reduction in the iodine value of the unsaturatedfractions recovered in the na1 product.

Efciency ofseparation is often sacrificed by reducing the temperaturesemployed in the lower portion of the tower and in order to prevent anexcessive thermo-alteration of the unsaturated acids. y 1

An object, of the present invention is toxprovide a method forseparating to a substantial degree the saturated from the unsaturated`acids without-thermo-alterattion of the unsaturated fraction separatelyAO'ther specinc objects and advantages will appear as the specificationproceeds.

The invention` is illustrated, in a preferred embodiment, by theaccompanying drawing, in which the single figure represents,diagramvmatically, the method and certain of the apparatus employed incarrying out the process.

'Ihe new method comprises the broad steps of first separating thesaturated fraction from the unsaturated fraction to a fair orsubstantial degree by means which do not subject the unsaturatedfraction to high temperatures likely tov produce thermo-alteration, andthen subse- 'quently fractionally distilling the saturated from theunsaturated fraction. Y

Any suitable means for separating the'saturatedsfrom the unsaturatedswithout the employment of such injurious high temperatures may beemployed. The fatty acids ay be crystallized with or without solvents ordiluents and the solid fraction. consisting predominantly of saturatedsthus separated from the soluble 'or liquid fractionv consistingpredominantly of 'unsaturateds Another method for separating thesaturateds from the unsaturateds without the employment of hightemperature isl by selective adsorption. The-mixtures of fatty acids aretreated with large quantities of a surfacev active material which tendsto adsorb the saturateds but not the unsaturateds.V Other vmethods forproducing a separation of the saturated acids from the unsaturated acids.to a substantial deacids and 'then subsequently fractionauy disto-10ling thesaturated fractions and the unsaturated fractinns separately. A-further object is to `provide a method and means for separatelyfractionally distilling saturated acids with an accompanying high yield.A further object is to provide a method and means for separatelyfractionally distilling unsaturated acids under conditions which obviatethermo-alteration while producing a greater yield of the high iodinefraction. Still another object is to provide a method and means foreffecting a substantial separation between saturated and unsaturatedfatty acids without the employment of high temperatures and thuspreserving unaltered the .iodine value of the `unsaturated fracsree willoccur to those skilled in the art and vmay be employed so long as hightemperatures deleterious to the iodine value of unsaturated fractionsare avoided.

AsV illustrative of the process, we will describe herein specificallythe method of separation v ...wherein crystallization is'the meansemployed. Fractional crystallization of saturated fatty acids fromunsaturated fatty -acids may be accomplished by simply cooling a fattyacid mixture containing preferably a relatively low amount of saturatedacids, such as, for example, 10% or less, to a temperature at vwhichpartialcrystallization occurs. The crystallized fracte tion may beseparated then by filtering or other' means.

We have found that a mnupmmqre effective 'separation of the saturatedsfrom the unsaturateds can be produced through .the use of solcontactwith liquid butane which the solvent before vents in coniunctionmitlLthe crystallizing Step anu further, that solvents which differsubstantially in density from the density of fatty acids increase theformation of crystals free from occluded. normally-llquidfatty acidswith the result that a sharper separation of saturateds. fromunsaturatetis is brought about.' For example, low density solventshaving a density not above 0.63, anchas butane, propane or pentane; suchdensity beingL well below that of fatty acids, are extremely effectivein promoting a satisfactory crystal growth. Such crystals'l may beallowed to separate xt by their own weight or, when placed in acentrifugal machine or in a filter, permit the liquid phase to bereadily and sharply separated therefrom. t

In crystallizing fatty acids, it is found that the solid phase iscomposed of mixed crystals' of fatty acids in which the saturated fattyacids o are to be found "lh higher iconcentration than in the originalmixture of fatty acids. In the absence of solvents, the normally liquidunsat urated fatty acids tend to become occluded with covered, theliquid phase consisting 4almost en-4 tirely of the unsatia'ted fattyacids passed from the separator through a heater, -preferably of thetubular type. to the fractionating column A. The solid phase consistingalmost entirely of the saturated acids ispassedthrough a similar heaterinto asimilar frctlonating column B. It

' will be understoodwthaa'if desired, a single fracthe normallycrystallinesaturated fatty acids.

When low areemployed, we nnd that there is asubstandensity solvents ofthe type described tially complete elimination of occludedY unset.T

urated fatty acids from the crystalline phaser We dnd-that the higherthe'ratioof solvent tofatty acid, the freer is the crystalline phase ofoccluded unsaturated fatty acids.

'In a specific description of the-method, `butane, which has a densityof approximately 0.58, will be referred to as the solvent or' diluent.

The mixture of fatty acids or fatty acid stock is introduced into amixer and there brought into der pressure into the mixer from acompressor or pressure reservoir. It is important that the fatty acidmixture be completely dissolved in allowing crystallization to proceed.The butane may be mixed with the fatty acids in theproportion of fivevolumes of butane to one volume of fatty acidmixture, or in any thersuitable proportion. From the mixer, the 'terial goes tn thecrystallizer where the temperature is reduced to-a point at whichcrystallization occurs. The crystallization may be produced by anysuitable cooling method. In the illustration given, .crystallization isinduced by allowing a portion of thetbutane to evaporate, the evaporatedbutanegbeing recovered and returned to the compressoror-p s'surereservoir. It will be that the butane may also be recovered fromportions of matemeans not shown.` Riecovery stills, compressors andpressure reservoirs arewell-knowntothoseskllledintheartforlammala-.hrecover! purposes and need not be shown mcthemmisfarmeditnafattyacidsthusrecovered frolnthe is forced untionating column may beemployed and the liq'- uid phase passed through the column at one timeand subsequently the solid phase treated in the fractionating tower. Iftwo towers are employed, as illustrated, it will be found that a lessernumber of bubble trays are required in tower A.

In the case of either fractionating tower A or fractionating tower B,the introduced charging stock of unsaturated fatty acids or saturatedfatty acids is first passedthrough the tube heater, as in the usualpractice, and thence'into the fractionating tower. The fractionatingoperation is carried on by passing' the vapors upwardly through thebubble trays as reflux liquid flows downwardly over the trays. A vacuumof approximately 5 mm. is preferably maintained at the top of the tower,while the pressure in the lower portion of the tower may be from 35 to40 mercury absolute but it is preferably appreclably lessthan 3 5 mm.Heat is introduced through the coils"by the circulation of Dowtherm"fluid or other suitable heating means-tn produce the desiredvaporization. Steamdsintroduced preferably in the lower portion'of thetower. A portion of the bottoms from the tower 'in the present instanceconsist, in the case of tower A, almost entirely `of unsaturated acidsSeparated alfCOldng 00 their Chain length and,

V in the case of tower B, of saturated fatty acids separated accordingto chain length. v

-As a specific example, sardine fatty acids were separated by theprocess described. being first mixed with five volumes of butane topnevolume of fatty acid and then refrigerated by permitting the butane toevaporate. The liquid phase was removed by withdrawing it from thesettled saturated Vacid crystals and after the removal of all solventremaining therein, is passed through the tube heater and thence intotower A. The

distillate fraction obtained from tower A constituted 50% of theoriginal sardine fatty acid mixture and had same sardine fatty acidmixture" when not subjected to the crystallizing andiseparationoperation andwhen fractionally distilled together gave only a 20% yieldat an iodinevalue of 254. Since the high iodine fraction is by farthe'most important product recovered from 'the processing of the oil.the value of the preliminary stepof separating the Aunsaturateds fromthe sahirateds without heat treatmentxthus becomes apparent.

with respect to the saturateds and senttotowerB or'passedthmugliYtowerainaseparaterlmhlsresultedina much increased yield sincetemperatures mid be raisedfr beyond those formerly employedinviewofthefactthatthere werepresmtsubstantially-no unsaturateds toundergo. thermal changeduetothehighheat.`

In the` distillation separately.- of the unsaturateds,itwasfoundthata-twerequippedemy with three trays might ntisfatorlly be ern-,

ployedsthus enabling a much-higher vacuumlf and lower distillationtemperahires to be used.

solidphaseeonsistingdf an iodine value of 254. The

In connection with the foregoing fractional distillation process, itlwill be notedv that the low density solvents already describedareuseful/not only for separating saturateds from unsaturateds but alsounsaturated fatty acids of comparatively low degree from unsaturatedfatty acids possessing a high degree'of unsaturation. For example, theprocess will result in some separation of linolic acid from oleic acidacommercially desirable separation.

While in )the foregoing description, we have referred to crystallizationas an example of a method whereby separation of the saturated fattyacids from the unsaturated may be accomplished without the useV ofdestructively high temperatures, itv will be understood that othermethods may be utilized for producing the same i results. As alreadymentioned. selective adsorption may be used. Itxis found that certainsur-- face active 'materials may be used which will select ,or adsorbthe saturateds while not aifecting substantially the unsaturateds.. As aspecific example, if fatty acids, preferably v admixeci with a solvent,are passed through va long layer ofv anhydrous aluminum oxide, thesaturated fraction will be retained in the layer while the unsaturatedspass through the filter. Any suitable adsorbents such as alumina,charcoal,

bleaching earth, gypsum, calcium carbonate,

magnesium nude, finely divided clay and other inorganic or organicmaterials may be used.

The portion passing tln'ough the lter may be sent to tower A after theremoval of the solvent while the adsorbed fraction may be recovered inthe usual manner and sent to tower B.

We claim: Y 1

1. In a method for treating a mixture of saturated and unsaturated fattyacidsincluding relatively low boiling saturated fatty acids andrelatively high boiling highly unsaturated fatty acids, to obtain a.high yield of highly unsaturated fatty acids, the steps'of subjectingthe mixture to low temperatures to bring' about crystallization of asaturated acid portion, sepa- `rating the crystallized saturated portionfrom the uncrystallized unsaturated portion, and sep-'i aratelyfractionally distilling said unsaturated fatty acid portion, withoutimparting sufiicient heat to the same to produce substantialthermoalteration of the unsaturated fatty acids, to obtain a pluralityof fractions of said portion of different boiling points, including arelatively large' high boiling fraction consisting predominantly ofhighly unsaturated fatty acids.

2. Inl a process for treating a mixture of .saturated and unsaturatedfatty acids including relatively low boiling saturated fatty acids andrelatively high boiling unsaturated fatty acids,

withdrawing from 'said pools a fraction consisting predominantly ofunsaturated fatty acids of iiigher boiling point than said low boilingfrac- 3. In a method for treating a mixture of saturated and unsaturatedfatty acids 'including relatively low boiling lsaturated fatty acids andrelatively high boiling unsaturated fatty acids, to obtain a high yieldof highly unsaturated fatty acids, the steps of mixing said fatty acidswith a solvent, reducing the temperature of the mixture to crystallize asaturatedl acid portion, separating the crystallized saturated portionfrom the uncrystallized unsaturated portion, .and treating separatelythe unsaturated fatty acid portion by vaporizing portions thereof andsubjecting such vapors under reduced pressure to contact with a seriesof heat exchanging pools of condensed fatty acid mixtures havingsucces'- sively lower boiling points, the pressure to which said vaporsare subjected being so low that the boiling point of the fatty acids inthe portion being treated at such pressures is below the temperature atwhich substantial thermo-alteration of the unsaturated fatty acids insuch portion occurs, condensing the low boiling vapors ,passing throughthe last of said pools, returning a portion of said condensed lowboiling vapors to said pools as reflux liquid, and withdrawing from saidpools a fraction of fatty acid of higher boiling point than said lowboiling fraction.

- 4. In a method for treating a mixture of saturated and unsaturatedfatty acids, including relatively low boiling saturated fatty acids andrelatively high boiling highly unsaturated fatty acids, to obtain a highyield of highly unsaturated fatty acids, the steps of mixing said fattyacids with a solvent, separating the mixture into two portions, one ofthe portions containing a predominant proportion of saturatedfatty acidsand the other portion containing a predominant proportion of unsaturatedfatty acids, the separation being carried out at temperaturessubstantially below those at which thermo-altera-A tion of vthe fattyacids occurs, and fractionally distil'ling said unsaturated fatty acidportion,` without imparting sufficient heat to the same to producesubstantial thermo-alteration of the unsaturated fatty acids, to obtaina plurality of fractions of said p0rtion of different boiling points,including a relatively large high boiling fraction consistingpredominantly of highly unsaturated fatty acids.

5. Ina method for treating a mixture of saturated and unsaturated fattyacids including relatively low boiling saturated fatty acids andrelatively high boiling unsaturated fatty acids,

the steps ofmixing the fatty acid mixture with y j contact with a'series ofheat exchanging pools of condensed fatty acid mixtures havingsuccessively lower boiling points, the heat imparted to said vaporsbeing insufficient to produce substantial thermo-alteration ofl theunsaturated fatty acids. condensing the low boiling vapors passingthrough the last ofsaid pools, returning a portion of said condensed lowboilto obtain a high yield of unsaturated fatty acids,

the steps of mixing said fatty acids with a solvent, separating themixture into two portions, one of the portions containing a predominantproportion of saturated fatty acids and the other portion containing apredominant proportion of unsaturated fatty acids, the separation being'carried out at temperatures substantially below those at whichthermo-'alteration of the fatty acids occurs, and treating separatelythe unsat-v urated fatty acid portion by vaporizing, portions thereofand subjecting such vapors under reduced pressure to contact with aseries of heat exchanging pools of condensed fatty acid mixtures ingvapors to said `pools as 'reflux liquid, and 75 havingsuccessively lowerboiling points, the heat imparted to saidfvapors being insuillcient toproduce substantial thermo-alteration of the unsaturated fatty acids,condensing the low boil.

i A "ing vapors passing through the last of said iheaiito umtedlndrelatively high boiling highly unsaturated fatty acids, to obtain a highvyield of highly -unsat- I -urated fatty. acids, the steps of firstseparating the mixture into two portions, one of the portions containinga predominant proportion of saturated fatty acids and the other portioncontaining a predominant proportion of unsaturated fatty acids, theseparation being carried out Vat temperatures substantially below thoseat which thermo-alteration of the fatty acids occurs, and fractionallythe unsaturated fatta acid portion, without imparting sumcient i thesame to produce substantial thermoalteration of the unsaturated fattyacids, to ob- Y tain a plurality, of fractions of said portion of.different boiling Points, includingI a relatively large high boilingfraction, consisting predominantly-of highly unsaturated fatty acids.

'1. Ina method for treating a mixture of vsath unsaturatedfattyacids'including relatively low boiling saturated fatty acids'andrelatively nigh mmm aman-.tea mty acids. to obtain a high yield ofunsaturated fatty acids,

the steps of first separating the mixture into two portions. one of the'portions containing a pre-v dominant proportion of saturated fatty acidsand the other poridon containing a predominant proportion of unsaturatedfatty acids. the separation being carried out at temperaturessubstantially below those at-'whichthermo-alteration of the fatty acidsoccurs, snd'treating sepa. rately theunsaturated fatty acid -portion byvaporising. portions thereof and subjecting such vapors under reducedpressure to contact with a series of heat exchanging P0018 of. condensedfatty acid having successively lower boiling points, the pressurest'o-which said vapors are subjected being so low-that the boiling pointof the fatty acids -in perature at which substantial thermo-alterationof the .unsaturated fatty acids occurs, condens- .last of said pools,returning a portion of said' ing-the low boiling vapors passing throughthe condensed lo'rwboiling vapors t0 said pools as reilux liquid, andwithdrawing frein said pools L a relatively large fraction consistingpxedomi-v,

nantly of fatty acids of higher boiling point than 'said lowboilingfraction.

ALBER Y fr H. mama. peut vs'rmom. Jaime is.V man.

the unsaturated heing treated at is below the tem

